When to use "Only PSA, Update Subsequently in Data Targets"?

We load data to a master data, in the InfoPackage, under the 3rd tab "Processing", in most cases, the 1st radio button "PSA and then in the InfoObject (Package by Package)" is usually checked. But sometimes we can see someone would like to check 3rd radio button "Only PSA, Update Subsequently in Data Targets", we wonder in which case to use this 3rd radio button?

Thanks!